The present invention provides novel oligomeric vinyl ester resins containing triazine groups or containing both triazine and oxazoline groups, as well as cured compositions prepared from said vinyl ester resins.
Vinyl esters are the reaction product of about equivalent amounts of a monounsaturated monocarboxylic acid and a polyepoxide. One class of vinyl esters is described by Bearden in U.S. Pat. No. 3,367,992 where dicarboxylic acid half esters of hydroxyalkyl acrylates or methacrylates are reacted with polyepoxide resins. Bowen in U.S. Pat. Nos. 3,066,112 and 3,179,623 describes the preparation of vinyl esters from monocarboxylic acids such as acrylic and methacrylic acid. Bowen also describes alternate methods of preparation wherein a glycidyl methacrylate or acrylate is reacted with the sodium salt of a dihydric phenol such as bisphenol-A. Vinyl ester resins based on epoxy novolac resins are described in U.S. Pat. No. 3,301,743 to Fekete et al. Fekete et al describes vinyl esters where the molecular weight of the polyepoxide is increased by reacting a dicarboxylic acid with the polyepoxide resin as well as acrylic acid, etc. in U.S. Pat. No. 3,256,226. Other functional compounds containing a group which is reactive with an epoxide group, such as an amine, mercaptan and the like, may be utilized in place of the dicarboxylic acid. All of the above-described compositions, which contain the characteristic linkages ##STR1## and terminal polymerizable vinylidene groups are classified as vinyl esters and are incorporated herein by reference.
The vinyl ester is typically combined with a reactive diluent, a copolymerizable vinyl monomer, to alter the viscosity of the mixture, to vary the properties of the cured coating, or for other known reasons. Most any vinyl monomer may be employed which is copolymerizable with the unsaturated groups of the vinyl ester. Such monomers include both monovinyl and polyvinyl monomers. Typical monomers include the alkenyl aromatic monomers such as styrene, .alpha.-methylstyrene, vinyltoluene, t-butyl styrene and the like; and alkyl and hydroxyalkyl esters of acrylic and methacrylic acid such as methyl, ethyl, propyl, butyl, cyclohexyl and hydroxyethyl, hydroxypropyl and hydroxybutyl acrylates and methacrylates. In addition to the above, other monomers are especially useful for ultra-violet light curable systems such as 2-acetoxyalkyl acrylates; pentaerythritol di-, tri- or tetra-acrylates and the like and may be added in any order.
The vinyl ester and copolymerizable vinyl monomer blend is a crosslinkable vinyl ester resin which is cured by mixing in a free radical forming catalyst in an amount ranging from 0.1 to about 5 percent by weight, preferably 1 to 2 percent by weight. Examples of these catalysts are benzoyl peroxide, tertiary butyl hydroperoxide, methylethylketone peroxide and the like. It is frequently of value to add an accelerator such as N,N-dimethylaniline, cobalt naphthenate and the like.
Preparation of polyepoxides containing triazine groups is taught by R. E. Hefner, Jr. in copending application Ser. No. 547,537, filed 10-31-83 which is incorporated herein by reference. The process of this invention uses an easily prepared mixed cyanate of a diphenol or polyphenol. More specifically, the process disclosed therein comprises reacting at least one material having an average of more than one aromatic hydroxyl group per molecule with at least 0.01 but not more than 0.95, preferably from about 0.05 to about 0.55, moles of cyanogen halide or mixture of cyanogen halides per aromatic hydroxyl group in the presence of a suitable base in a quantity of from about 0.01 to about 1.1, preferably from about 0.05 to about 0.6, moles per aromatic hydroxyl group at a temperature and time sufficient to essentially complete the reaction and thereafter recovering the resultant cyanate mixture; trimerizing the cyanate mixture in the presence of a suitable trimerization catalyst at a temperature and time to essentially complete the trimerization reaction; epoxidizing the resultant trimerized product in a conventional manner by reaction with an epihalohydrin with subsequent dehydrohalogenation with a basic-acting material and finally recovering the resultant triazine functional glycidyl ether product. Excellent control over the molecular weight and content of triazine groups is provided by this process. The epoxy resin compositions of this invention possess unusually high thermal stability as well as excellent overall physical and mechanical properties.
Preparation of polyepoxides containing triazine and oxazoline groups is disclosed in copending application Ser. No. 576,304 filed Feb. 2, 1984. The process disclosed therein uses the aforementioned mixed cyanate of a diphenol or polyphenol. Co-oligomerization of this cyanate mixture with an epoxy resin such as the diglycidyl ether of bisphenol A, provides hydroxyaromatic oligomers containing both triazine and oxazoline groups. Oligomers prepared from co-oligomerization of the mixed cyanate of a diphenol with an epoxy resin using mole ratios of epoxy groups to nitrile groups of about 1 to 10 to about 1 to 40 or more are most preferred in the process of this invention. The oligomers, and unreacted diphenol, if any, are then epoxidized using methods well known in the art. The epoxy resin compositions of this invention possess excellent thermal stability as well as enhanced mechanical properties.
The vinyl ester compositions of the present invention contain triazine groups or both triazine and oxazoline groups and are derived by reaction of the respective triazine functional or triazine and oxazoline functional epoxy resins with a monounsaturated monocarboxylic acid. The invention consists of the vinyl esters and the vinyl ester and copolymerizable vinyl monomer formulations, whether or not cured.